Thermal ink jet ink composition

ABSTRACT

A thermal ink jet ink composition includes one or more volatile organic solvents, wherein the one or more volatile organic solvents are selected from C 1 -C 4  alcohols, C 3 -C 6  ketones, C 3 -C 6  esters, C 4 -C 8  ethers, and mixtures thereof; one or more humectants, wherein the humectants are present in an amount not more than 30% by weight of the ink composition; one or more binder resins; and one or more dyes. The ink composition is suitable for use in a thermal ink jet printer and the ink composition has a slow rate of kogation such that it is capable of being printed at least 10 million drops per nozzle from the thermal ink jet printer before drop weight of the ink composition is reduced by more than 10%.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation-In-Part of U.S. application Ser. No.12/646,162 filed Dec. 23, 2009, which is a Continuation-In-Part of U.S.application Ser. No. 12/059,753 filed Mar. 31, 2008, both of which areincorporated herein by reference in their entireties.

BACKGROUND OF THE INVENTION

Thermal ink jet (TIJ) print heads produce ink droplets from thermalvaporization of the ink solvent. In the jetting process, a resistor isheated rapidly to produce a vapor bubble which subsequently ejects adroplet from the orifice. This process is extremely efficient andreproducible. Modern TIJ print heads for industrial graphicsapplications are capable of generating uniform drops of 4 pL or smallerin volume at frequencies of up to 36 kHz or greater. Typical commercialTIJ devices are specifically designed to vaporize water or solvents thathave physical properties close to those of water (e.g. high boilingpoint, large heat capacity, low molecular weight).

Although TIJ printing systems have been available for over 30 years,nearly all of the commercial inks available for thermal ink jet systemshave been water-based, i.e. they contain more than 50% water. Suchaqueous inks have one or more drawbacks such as long ink dry times orpoor adhesion to semi-porous or non-porous substrates.

There is a desire for inks with attractive performance characteristicssuch as short dry times, long decap times and good adhesion when using aTIJ system to print onto semi-porous and non-porous substrates.

BRIEF SUMMARY OF THE INVENTION

The disclosure provides a thermal ink jet ink composition including oneor more volatile organic solvents, one or more humectants, one or morebinder resins, and one or more dyes. The one or more volatile organicsolvents are selected from C₁-C₄ alcohols, C₃-C₆ ketones, C₃-C₆ esters,C₄-C₈ ethers, and mixtures thereof. The humectants are present in anamount not more than 30% by weight of the ink composition. The inkcomposition is suitable for use in a thermal ink jet printer and the inkcomposition has a slow rate of kogation such that it is capable of beingprinted at least 10 million drops per nozzle from the thermal ink jetprinter before drop weight of the ink composition is reduced by morethan 10%.

In another aspect, the disclosure provides a printing system including athermal ink jet cartridge containing a thermal ink jet ink composition.A thermal ink jet print head is adapted to direct a stream of dropletsof the ink composition to a substrate. The thermal ink jet inkcomposition has a decap time of at least 15 seconds and a dry time ofless than 5 seconds on a non-porous substrate when used in the thermalink jet print head.

The disclosure also provides a thermal ink jet cartridge including athermal ink jet ink composition.

The thermal ink jet ink composition of the invention has one or more ofthe following features: short dry times, long decap times, good adhesionto substrates, safety, and material compatibility with the inkcartridge. The preferred ink composition is one that has a slow rate ofresistor buildup by using suitable binder resins, colorants, andadditives. Decap time at the droplet level is the length of time that anozzle can remain dormant and then be fired again without anysignificant reduction in droplet velocity, reduction in droplet weight,or change in droplet direction. Decap time at the print level ismeasured as the length of time that a print head can remain dormant andthen be fired again without any significant degradation of print. Aspecific example of a decap time measurement is the maximum amount ofidle time a system can undergo and still recover full nozzle functionwithin the first 20% of a printed stairstep image (i.e. 80% of the printis intact). Fluids with good material compatibility are defined as thosewhich do not degrade the ability of the TIJ cartridge to fire for somereasonable length of time that is meaningful to a customer. Kogation isa build-up on the print resistor that occurs after repetitive firings.The buildup reduces the rate of heat transfer from the resistor to theliquid ink. Kogation can reduce drop weight, change drop trajectory,lower drop velocity, or cause nozzles to become completely inactive. Thethermal ink jet ink composition does not require heat assist (e.g.,thermal driers) when printed on semi-porous and non-porous substrates.

DETAILED DESCRIPTION OF THE INVENTION

The invention provides a thermal ink jet ink composition comprising oneor more volatile organic solvents, one or more humectants, one or morebinder resins, and one or more colorants. A specific problem that occurswith TIJ inks is that of kogation. Kogation is a residue or build-upthat deposits on the TIJ firing resistors during use, thus impedingperformance via drop weight reduction, misdirected jets, or in extremecases causing complete loss of nozzle function. Kogation occurs duringhigh temperatures reached during repetitive resistor heating cycles andis usually attributed to materials or impurities in the ink thatdecompose, react, or become insoluble under these conditions.

In accordance with an embodiment, the thermal ink jet ink compositionincludes volatile organic solvents selected from C₁-C₄ alcohols, C₃-C₆ketones, C₃-C₆ esters, C₄-C₈ ethers, and mixtures thereof. The volatileorganic solvents are preferably selected from C₁-C₄ alcohols, C₃-C₆ketones, and mixtures thereof. Examples of C₁-C₄ alcohols includemethanol, ethanol, 1-propanol, and 2-propanol. Examples of C₃-C₆ ketonesinclude acetone, methyl ethyl ketone, methyl n-propyl ketone, andcyclohexanone. Examples of C₄-C₈ ethers include diethyl ether, dipropylether, dibutyl ether and tetrahydrofuran. Examples of C₃-C₆ estersinclude methyl acetate, ethyl acetate and n-butyl acetate. The organicsolvents, particularly alcohols, ketones, and esters, have an attractivefeature that they provide better solvency to common binder resins,penetrate semi- and some non-porous substrate surfaces more readily, andevaporate more quickly than water based inks, thus reducing dry time andimproving adhesion.

In particular embodiments the thermal ink jet ink compositions includes,as the volatile organic solvent(s), methyl ethyl ketone, ethanol, ablend of methyl ethyl ketone and methanol, or a blend of methyl ethylketone and ethanol as the primary jetting solvent. Many commercial inksfor non-thermal ink jet applications use methyl ethyl ketone due to itsstrong solvation properties, preferred surface tension, and fast drytimes. The solvent strength of methyl ethyl ketone gives methyl ethylketone-based inks access to a wide selection of colorants, resins,co-solvents and additives that are unavailable to weaker solvents, suchas alcohols.

The solvent-based thermal ink jet inks disclosed herein preferably haveviscosities below 3 cPs, preferably below 2 cPs, at 25° C. Many methylethyl ketone-based inks that are optimized for other ink jettechnologies (such as continuous ink jet (CIJ) or drop-on-demand (DOD))jet poorly or not at all in thermal ink jet cartridges. Existing CIJinks have high resin and/or dye content (and overall high solids),leading to relatively high viscosities of typically 2 to 5 cPs at 25° C.High molecular weight polymers may also impede thermal ink jet jettingperformance when used at levels that are typically found in commercialCIJ inks. Careful screening of materials for potential kogation is animportant step in thermal ink jet ink evaluation. Existing CIJ inks, ifthey can be jetted in thermal ink jet systems, have very short decaptimes (less than 5 or 10 seconds), which makes them commerciallyinfeasible. Inks with very short decap times can create unrecoverablenozzle blockages in thermal ink jet systems and thus lead to prematurecartridge failure before target delivered ink volume and expectedcartridge end of life is reached. Thus, specific materials andformulation levels are required to create solvent-based thermal ink jetinks that jet well, have good long term reliability, have manageabledecap times and do not cause resistor kogation while maintaining shortdry times, crisp print quality and excellent adhesive performance onnon-porous substrates.

The total amount of the one or more volatile organic solvents can be inany suitable amount, for example, in an amount 50% or more, about 60% ormore, about 70% or more, about 80% or more, or about 90% or more byweight of the ink jet ink composition. In an embodiment, the totalamount of one or more volatile organic solvents can be present in anamount from 50% to about 99%, preferably from about 60% to about 95%,and more preferably from about 70% to about 90% of the ink jet inkcomposition. In one embodiment, if water is present in the thermal inkjet ink composition, it is present in an amount up to 49% by weight, upto about 25% by weight, up to about 10% by weight, up to about 5% byweight, or up to about 2% by weight of the ink jet ink composition.

In an embodiment, the one or more volatile organic solvents includemethyl ethyl ketone and one or both of ethanol and methanol. The methylethyl ketone may be present in an amount up to 90% by weight, up to 85%by weight, or up to 80% by weight of the ink jet ink composition. Themethyl ethyl ketone may be present in an amount of at least 60% byweight, at least 70% by weight, or at least 75% of the ink jet inkcomposition. The ethanol or methanol may be present in an amount up to90% by weight, up to 85% by weight, or up to 80% by weight of the inkjet ink composition. The ethanol may be present in an amount of at least70% by weight, at least 80% by weight, or at least 85% of the ink jetink composition.

The thermal ink jet ink composition can include any suitable colorant orcolorants, which may be dye or pigment. In an embodiment, one or moredyes are employed as the colorant, wherein the one or more dyes areselected from the group consisting of acid dyes, basic dyes, solventdyes, disperse dyes, mordant dyes, reactive dyes and any combinationthereof. Examples of solvent dyes include naphthol dyes, azo dyes, metalcomplex dyes, anthraquinone dyes, quinoimine dyes, indigoid dyes,benzoquinone dyes, carbonium dyes, naphthoquinone dyes, naphthalimidedyes, phthalocyanine dyes, nigrosine dyes and perylene dyes.

For example, the thermal ink jet ink composition can include one or moredyes selected from the group consisting of C.I. Solvent Yellow 19, C.I.Solvent Yellow 21, C.I. Solvent Yellow 61, C.I. Solvent Yellow 80, C.I.Solvent Orange 1, C.I. Orange 37, C.I. Orange 40, C.I. Solvent Orange54, C.I. Solvent Orange 63, C.I. Solvent Red 8, Solvent Red 49, C.I.Solvent Red 81, C.I. Solvent Red 82, C.I. Solvent Red 84, C.I. SolventRed 100, C.I. Acid Red 92, C. I. Reactive Red 31, Orient Pink 312, C.I.Basic Violet 3, C.I. Basic Violet 4, C.I. Solvent Violet 8, C.I. SolventViolet 21, C.I. Solvent Blue 2, C.I. Solvent Blue 5, C.I. Solvent Blue11, C.I. Solvent Blue 25, C.I. Solvent Blue 36, C.I. Solvent Blue 38,C.I. Solvent Blue 55; C.I. Solvent Blue 70, C.I. Solvent Green 3, C.I.Solvent Black 3, C.I. Solvent Black 5, C.I. Solvent Black 7, C.I.Solvent Black 22, C.I. Solvent Black 26, C.I. Solvent Black 27, C.I.Solvent Black 29 (VALIFAST BLACK 3808 or ORASOL BLACK RLI™), C.I. AcidBlack 123, C.I. Solvent Black 48 (MORFAST BLACK 101™), C.I. Oil Blue613, and any combination thereof, and preferably one or more dyesselected from the group consisting of C.I. Solvent Black 29 (ORASOLBLACK RLI™), C.I. Solvent Black 27, C.I. Solvent Black 48, C.I. SolventBlack 3 (Oil Black 860), C.I. Basic Violet 3, C.I. Solvent Blue 38, C.I.Solvent Blue 70, C.I. Oil Blue 613, C.I. Solvent Red 49 (ORIENT PINK™312), C.I. Solvent Orange 54 (VALIFAST ORANGE™ 3210), and anycombination thereof.

Any suitable pigment can be used, for example, one or more pigmentsselected from the group consisting of phthalocyanine blue, carbon black,mars black, quinacridone magenta, ivory black, prussian blue, cobaltblue, ultramarine blue, manganese blue, cerulean blue, indathrone blue,chromium oxide, iron oxides, viridian, cobalt green, terre verte, nickelazo yellow, light green oxide, phthalocyanine green-chlorinated copperphthalocyanine, burnt sienna, perinone orange, irgazin orange,quinacridone magenta, cobalt violet, ultramarine violet, manganeseviolet, dioxazine violet, zinc white, titanium white, flake white,aluminum hydrate, blanc fixe, china clay, lithophone, arylide yellow G,arylide yellow 10G, barium chromate, chrome yellow, chrome lemon, zincyellow, cadmium yellow, aureolin, naples yellow, nickel titanate,arylide yellow GX, isoindolinone yellow, flavanthrone yellow, yellowochre, chromophthal yellow 8GN, toluidine red, quinacridone red,permanent crimson, rose madder, alizarin crimson, vermilion, cadmiumred, permanent red FRG, brominated anthranthrone, naphthol carbamide,perylene red, quinacridone red, chromophthal red BRN, chromophthalscarlet R, aluminum oxide, bismuth oxide, cadmium oxide, chromium oxide,cobalt oxide, copper oxide, iridium oxide, lead oxide, manganese oxide,nickel oxide, rutile, silicon oxide, silver oxide, tin oxide, titaniumoxide, vanadium oxide, zinc oxide, zirconium oxide, and any combinationthereof.

In embodiments, the pigments are selected from the group consisting ofazo pigments, phthalocyanine pigments, quinacridone pigments, dioxazinepigments, isoindolinone pigments, metal oxide pigments, carbon black,and any combination thereof. The pigments can have any suitable particlesize, for example, from about 0.005 micron to about 15 microns,preferably from about 0.005 to about 1 micron, and more preferably fromabout 0.01 to about 0.3 micron.

In any of the embodiments, the colorant, dye or pigment, can be presentin an amount from about 0.01% to about 10%, preferably from about 0.5%to about 7%, and more preferably from about 1% to about 5% by weight ofthe ink jet ink composition.

In any of the embodiments, any suitable humectant can be used.Humectants are additives which maintain a wet environment in thevicinity of the ink jet nozzle during the evaporation process, thusextending the decap time. Preferably, humectants have a boiling pointgreater than 150° C., greater than 200° C., or greater than 250° C.,and/or a relative evaporation rate (with n-butyl acetate=1) less than1.0, less than 0.9, less than 0.7, less than 0.4, less than 0.1, or lessthan 0.01. The humectants typically are solvents having one or morepolar functional groups such as hydroxyl, ether, amide, ester, ketone,and carbonate, for example, two functional groups, which may be the sameor different, such as two hydroxyl groups or one hydroxyl group and oneether group. In an embodiment, the one or more humectants are selectedfrom the group consisting of polyols, glycol ethers, glycol etheracetate, diacetone alcohol, 2-pyrrolidinone, N-methylpyrrolidinone,ethyl lactate, butyl lactate, propylene carbonate,1,3-dimethyl-2-imidazolidindione, and alkyl esters, and any combinationthereof.

For example, the polyol is selected from the group consisting ofpolyethylene glycol, polypropylene glycol, poly(ethylene-co-propyleneglycol), trimethylol propane, ethylene glycol, glycerin, diethyleneglycol, triethylene glycol, tripropylene glycol, tetraethylene glycol,pentaethylene glycol, 1,2-propylene glycol, 1,3-propanediol, butyleneglycol, triethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexyleneglycol, bis-2-hydroxyethyl ether, 1,4-butanediol, 1,2-butenediol,1,4-butenediol, 1,3-butenediol, 1,5-pentanediol, 2,4-pentanediol,2,4-heptanediol, 1,8-octanediol, 1,10-decanediol, 1,12-dodecanediol,1,4-cyclohexanediol, 1,4-cyclohexanedimethanol,1,2-bis(hydroxymethyl)cyclohexane, 1,2-bis(hydroxyethyl)-cyclohexane,3-methyl-1,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, neopentylglycol, pentaerythritol, sorbitol, mannitol, and any combinationthereof, and preferably the polyol is selected from the group consistingof polyethylene glycol, trimethylol propane, ethylene glycol, propyleneglycol, glycerin, diethylene glycol, tripropylene glycol, and anycombination thereof,

A preferred humectant is glycol ether, for example, a glycol etherselected from the group consisting of ethylene glycol monomethyl ether,ethylene glycol monoethyl ether, propylene glycol monomethyl ether,tripropylene glycol monomethyl ether, ethylene glycol monobutyl ether,diethylene glycol monomethyl ether, diethylene glycol monoethyl ether,propylene glycol n-propyl ether, propylene glycol t-butyl ether,propylene glycol n-butyl ether, dipropylene glycol methyl ether,dipropylene glycol n-propyl ether, dipropylene glycol t-butyl ether,dipropylene glycol n-butyl ether, tripropylene glycol n-propyl ether,tripropylene glycol t-butyl ether, tripropylene glycol n-butyl ether,ethyl cellosolve, methyl cellosolve, polyethylene glycol monomethylether, polypropylene glycol monomethyl ether, methoxytriglycol,ethoxytriglycol, butoxytriglycol, 1-butoxyethoxy-2-propanol, ethyleneglycol phenyl ether, propylene glycol phenyl ether, diethylene glycolphenyl ether, polyethylene glycol phenyl ether, and any combinationthereof, and preferably, the glycol ether is selected from the groupconsisting of ethylene glycol monomethyl ether, ethylene glycolmonoethyl ether, propylene glycol monomethyl ether, propylene glycolmonopropyl ether, tripropylene glycol monomethyl ether, ethylene glycolmonobutyl ether, diethylene glycol monomethyl ether, diethylene glycolmonoethyl ether, and any combination thereof. In certain embodiments,propylene glycol monopropyl ether (Dowanol PnP) is a preferredhumectant. In other embodiments, propylene glycol monomethyl ether(Dowanol PM) is a preferred humectant. In other embodiments, diacetonealcohol is a preferred humectant.

Humectants contribute, at least in part, to a feature of the thermal inkjet ink composition. Thus, humectants can lengthen decap times; however,excessive amounts of humectants could increase the dry time of the inkjet ink composition. In any of the embodiments, the one or morehumectants can be present in any suitable amount, for example, in anamount about 30% by weight or less, about 25% by weight or less, about20% by weight or less, about 15% by weight or less, or about 10% byweight or less, of the ink composition. In an embodiment, the one ormore humectants are present in an amount at least about 1% by weight, atleast about 2% by weight, at least about 5% by weight, or at least about10% by weight of the ink composition. In an embodiment, the one or morehumectants can be present in an amount from about 1% to about 30% byweight, preferably from about 5% to about 25% by weight, and morepreferably from about 10% to about 20% by weight of the ink jet inkcomposition.

As discussed, the thermal ink jet ink composition includes one or morebinder resins. Any suitable binder resin, soluble or dispersible, can beemployed, preferably a solvent soluble binder resin. In an embodiment,the thermal ink jet ink composition includes one or more binder resinsselected from the group consisting of polyamide resins, polyurethaneresins, rosin ester resins, acrylic resins, polyvinyl butyral resins,polyesters, phenolic resins, vinyl resins, styrene/acrylate copolymers,cellulose ethers, cellulose nitrate resins, polymaleic anhydrides,acetal polymers, styrene/butadiene copolymers, styrene/methacrylatecopolymers, sulfonated polyesters, sulfonamide-modified epoxy resins,sulfonamide-modified formaldehyde resins, sulfonamide-modified melamineformaldehyde resins, aldehyde resins, polyhydroxystyrene resins andpolyketone resins, and any combination thereof, and preferably one ormore binder resins selected from the group consisting of cellulosenitrate resins, polyamide resins, rosin ester resins, acrylic resins,polyvinyl butyral resins, vinyl resins, polyhydroxystyrene resins,sulfonamide-modified epoxy resins, sulfonamide-modified formaldehyderesins, sulfonamide-modified melamine formaldehyde resins, and anycombination thereof. An example of a suitable polyamide resin is ARIZONA201-150™ available from Arizona Chemical Company, Jacksonville, Fla., orCOGNIS VERSAMID 756™, available from Cognis GmbH, Monheim am Rhein,Germany, both of which are alcohol-soluble polyamide resins. Examples ofwood rosin ester resins include UNIREZ™ 8115, available as a 40%solution in ethanol from Penn Color, Doylestown, Pa., which is ahydrogenated wood rosin ester, and STAYBELITE™ ESTER 10, available fromChem Central Corporation.

Examples of cellulose nitrate resins are NOBEL™ DLX 3-5 or NOBEL™ DHX5-8, available from Nobel Enterprises. Examples of polyvinyl butyralresins are PIOLOFORM™ BN18, available from Wacker Chemie AG, andMOWITAL™ B20H available from Kuraray America, Inc. Examples of acrylicand styrene/acrylic resins are Joncryl 611, 682, and 586 (available fromBASF, USA) and Paraloid B-66 and B-72 (available from Dow Chemical,USA). Examples of vinyl resins include UCAR VYHH, VMCH, YMCA, and VAGF(available from Dow Chemical Company, USA) and Vinnol E15/45, H14/36,E15/45M, and E16/40A (available from Wacker Chemie AG, Germany).Examples of polyhydroxystyrene resins include poly(p-hydroxy styrene)from DuPont. An example of a sulfonamide-modified epoxy resin is AD-PROMTS, available from Rit-Chem. Examples of sulfonamide-modifiedformaldehyde resins are P-TOLUENE SULFONAMIDE FORMALDEHYDE RESIN,available from Jiaxing Chenlong Chemical Company, Ltd. and RIT-O-LITEMHP, available from Rit-Chem.

It has been found that by using binder resins with certain properties,the amount of kogation can be reduced. Kogation is a residue or build-upthat deposits on the thermal ink jet firing resistors during use, thusimpeding performance via drop weight reduction, misdirected jets, or, inextreme cases, complete loss of nozzle function. Kogation occurs duringthe high temperatures reached during repetitive resistor heating cyclesand is usually attributed to materials in the ink that decompose, react,or become insoluble under these conditions. It has been found that byusing binder resins with good solubility properties in the solvent, theeffects of kogation can be greatly minimized. In particular, it has beenfound that certain resins are less prone to kogation in alcohol-basedinks; such resins include polyhydroxystyrene, styrene/acrylic resins,rosin-based resins, and synthetic ketone resins, sulfonamide-modifiedformaldehyde resins and sulfonamide-modified epoxy resins. Forketone-based inks, polymers which are less prone to kogation includenitrocellulose resins, acrylic resins, styrene/acrylic resins, urethaneresins, rosin-based resins, silicone resins, sulfonamide-modifiedformaldehyde resins and sulfonamide-modified epoxy resins.

Kogation may be determined by measuring the drop weight of ink ejectedfrom the nozzles. The onset of kogation can be defined as a consistentreduction in drop weight of greater than 10% from the initial dropweight after 5, 10, 15, 20, or 25 million drops per nozzle actuations.The drop weight loss is measured by jetting a fixed number of drops fora select subgroup of nozzles and monitoring the mass with a highprecision scale after each cycle. This process is repeated until thedesired level (e.g., 10 or 25 million drops per nozzle level) or higheris reached. A drop weight tester (available from ImTech, Inc.,Corvallis, Oreg.) may be used to perform these measurements. The thermalink jet ink compositions disclosed herein preferably resist kogationsuch that they can be printed at greater than 10 million drops pernozzle before significant kogation occurs, and more preferably greaterthan 15 million drops per nozzle, and even more preferably greater than25 million drops per nozzle.

The polymeric binder resin can be present in any suitable amount, forexample, in an amount from about 0.1 to about 30%, preferably from about0.2 to about 15%, and more preferably from about 0.3 to about 8% of theink jet ink composition. The polymeric binder resin may have a weightaverage molecular weight (M_(w)) of less than 250,000, less than100,000, less than 50,000, less than 25,000, less than 10,000, less than5000, and less than 3000. While not intending to be bound by theory, itis believed that resins with lower molecular weights tend to re-dissolvemore readily and tend to have better decap time when compared to highermolecular weight resins in the same solvent mixtures. Alternatively,sulfonamide-modified polymers resist kogation irrespective of molecularweight. While not intending to be bound by theory, the sulfonamide groupmay passivate the resistor surface and thus form a bather that impedeskogation.

In a particular embodiment of the thermal ink jet ink composition, thevolatile organic solvent or solvents can be present in an amount fromabout 50% to about 95% by weight, the colorant(s) (dyes, pigments, or acombination thereof), can be present in amount from about 1% to about 8%by weight, the humectant can be present in an amount from about 3% to30% by weight, and the binder resin can be present in an amount fromabout 1% to about 15% by weight of the ink jet ink composition.

The thermal ink jet ink composition can further include one or moreadditives such as surfactants, and plasticizers. Preferably, a polymericsurfactant is employed. Examples of surfactants include modifiedpolysiloxanes, alkyl modified polyoxyalkyleneamines, alkyl modifiedpropoxylated (poly(oxypropylene)) diamines, alkyl ether amines, nonylphenol ethoxylates, ethoxylated fatty amines, fluorinated organic aciddiethanolamine salts, alkoxylated ethylenediamines, alkyl modifiedpolyethylene oxides, alkyl modified polyalkyleneoxides, alkyl phosphateethoxylate mixtures, polyoxyalkylene derivatives of propylene glycol,and polyoxyethylated fatty alcohols. A specific example of a suitablepolymeric surfactant is Silicone Fluid SF-69, available from GeneralElectric, which is a blend of silanols and cyclic silicones. Anotherspecific example of surfactant is SILWET L-7622™ which is a siloxanepolyalkyleneoxide copolymer (Momentive Performance Chemicals, USA).Fluorosurfactants can also be used to modify surface properties.Examples of fluorosurfactants suitable for thermal inkjet compositionsinclude: Novec 4430 and Novec 4432 (available from 3M); Zonyl FSN, ZonylFSH, Capstone FS-34, Capstone FS-35, Capstone FS-3100 and Capstone FS-22(available from DuPont).

In any of the embodiments, the surfactants can be present in an amountfrom about 0.01 to about 2.0%, preferably from about 0.02 to about 1%,and more preferably from about 0.03 to about 0.5% of the ink jet inkcomposition.

Examples of suitable plasticizers include phthalate plasticizers, e.g.,alkyl benzyl phthalates, butyl benzyl phthalate, dioctyl phthalate,diisobutyl phthalate, dicyclohexyl phthalate, diethyl phthalate,dimethyl isophthalate, dibutyl phthalate, and dimethyl phthalate, esterssuch as di-(2-ethylhexy)-adipate, diisobutyl adipate, glyceroltribenzoate, sucrose benzoate, dibutyl sebacate, dibutyl maleate,polypropylene glycol dibenzoate, neopentyl glycol dibenzoate, dibutylsebacate, and tri-n-hexyltrimellitate, phosphates such as tricresylphosphate, dibutyl phosphate, polyurethanes, and sulfonamideplasticizers such as Plasticizer 8, available from Monsanto Co., St.Louis, Mo., which is n-ethyl o,p-toluene sulfonamide.

In certain embodiments, the plasticizer can be present in an amount fromabout 0.1 to about 5.0%, preferably from about 0.2 to about 3.0%, andmore preferably from about 0.25 to about 2.0% of the ink jet inkcomposition.

The thermal ink jet ink composition may include additional ingredientssuch as bactericides, fungicides, algicides, sequestering agents,buffering agents, corrosion inhibitors, antioxidants, light stabilizers,anti-curl agents, thickeners, dispersing agents, conductive salts, andother agents known in the relevant art. In an embodiment, the inkcomposition is free or substantially free of antioxidants.

The thermal ink jet ink composition has one or more attractive featuressuch as short unassisted dry times of printed alphanumeric or graphicimages, long decap times, good adhesion to semi-porous and non-poroussubstrates, safety, and material compatibility with one or morecomponents of a thermal ink jet printer. In particular, it is desirablethat the thermal ink jet ink composition have both a short dry time anda long decap time. For example, embodiments of the thermal ink jet inkcomposition have a dry time of about 10 seconds or less, such as 7seconds or less, 5 seconds or less, 4 seconds or less, or 2 seconds orless, on non-porous substrates under ambient conditions. Non-poroussubstrates include materials such as plastics, metals, glass, and glossypaper. On porous substrates, the dry times are shorter than in semi- ornon-porous substrates. For example, embodiments of the thermal ink jetink composition have a dry time of about 1 second on porous substratesand less than about 5 seconds, preferably less than about 2 seconds, andmore preferably less than about 1 second on semi-porous substrates. Thethermal ink jet ink composition preferably has a decap time of at least10 seconds, at least 15 seconds, at least 30 seconds, at least 45seconds, at least 60 seconds, or at least five minutes, when used in athermal ink jet print head. In a preferred embodiment, the thermal inkjet ink composition has a decap time of at least 15 seconds and a drytime of less than 5 seconds on non-porous substrates when used in athermal ink jet print head. Decap time at the microscopic (i.e. droplet)level can be described as the length of time that a nozzle can remaindormant and then be fired again without any significant reduction indroplet velocity, reduction in droplet weight, or change in dropletdirection. Decap time at the macroscopic (i.e. print) level is measuredas the length of time that a print head can remain dormant and then befired again without any significant degradation of print quality (i.e.,it is the maximum wait time between printing events with no significantchange to the printed image after the wait). A specific example of adecap time measurement is the maximum amount of idle time a system canundergo and still recover full nozzle function within the first 20% of aprinted stairstep image (i.e. 80% of the print is intact).

The thermal ink jet ink composition can have any suitable viscosity orsurface tension. In embodiments of the invention, the thermal ink jetink composition has a viscosity of less than about 10 cPs, preferablyless than about 5 cPs, more preferably less than about 3 cPs, and mostpreferably less than about 2 cPs, for example, a viscosity from about0.6 to 4 or from about 0.6 to about 3 cPs at 25° C. In embodiments ofthe invention, the thermal ink jet ink composition has a surface tensionfrom about 20 to about 50 mN/m, from about 21 to about 40 mN/m, or fromabout 22 to about 30 mN/m at 25° C. The solids content of the thermalinkjet ink composition may be less than 20% by weight, and is preferablyless than 15% by weight.

The thermal ink jet ink composition can be prepared by any suitablemethod. For example, the chosen ingredients can be combined and mixedwith adequate stirring and the resulting fluid filtered to remove anyundissolved impurities.

The thermal ink jet ink composition may used in any suitable thermal inkjet cartridge. The thermal ink jet cartridge is preferably fashionedfrom materials that are resistant to the solvents used in the thermalink jet ink composition. Suitable thermal ink jet cartridges aredisclosed in U.S. Patent Application Publication 20090303299A1, entitled“INK CONTAINMENT SYSTEM AND INK LEVEL SENSING SYSTEM FOR AN INKJETCARTRIDGE,” with a publication date of Dec. 10, 2009, and U.S. PatentApplication Publication 20100328398A1, entitled “THERMAL INKJET PRINTHEAD WITH SOLVENT RESISTANCE,” with a publication date of Dec. 30, 2010,the contents of which are hereby incorporated by reference.

The present disclosure further provides a method for printing images ona substrate in a thermal ink jet printer comprising directing dropletsof any of the embodiments of the thermal ink jet ink composition to asubstrate and allowing the ink droplets to dry, thereby printing imageson a substrate. Any suitable substrate can be printed in accordance withthe invention. Examples of suitable substrates include porous substratessuch as uncoated paper, semi-porous substrates such as aqueous coatedpaper, clay coated paper, silica coated paper, UV overcoated paper,polymer overcoated paper, and varnish overcoated paper, and non-poroussubstrates such as hard plastics, polymer films, metals, glass, coatedfoils, polymer laminates, foil laminates, and ceramics. The papersubstrates can be thin sheets of paper, rolls of paper, or cardboard.Plastics, metals, glass, foils, laminates and ceramic substrates can bein any suitable form such as in the form of bottles or containers,plates, rods, cylinders, etc.

Examples of polymer coating include a coating of polystyrene, polyvinylalcohol, polyacryate, polymethacrylate, polystryrene or polyvinylchloride. Examples of polymer film substrates include polyvinylbutyrals, polyolefins, polyvinyl chloride, polyethylene terephthalate,PETG, PETE, polybutylene terephthalate (PBT), polyester, polycarbonate,acrylonitrile-butadiene-styrene (ABS) copolymer, polyvinyl fluoridepolymer, polyamides, polyimides, and cellulose. Plastics can be treatedplastics (e.g. chemical etch, corona discharge, flame plasma, etc.) oruntreated plastics. Examples of metals include aluminum, copper,stainless steel, and metal alloys. Examples of ceramics include oxides,nitrides, and carbides of metals.

The following examples further illustrate the invention but, of course,should not be construed as in any way limiting its scope.

COMPARATIVE EXAMPLES

This example illustrates comparative examples of conventional continuousink jet formulations. The ink compositions of each of the ComparativeExamples were provided in a conventional thermal ink jet cartridge toattempt to jet the inks. Three commercial CU ink compositions fromVideojet Technologies Inc. (16-8200, 16-8470 and 16-8530) jetted verypoorly or not at all or have decap time of less than 5 seconds in thethermal ink jet cartridge. Thus, it can be seen that conventionalcontinuous ink jet ink compositions are not suitable for use in thermalink jet cartridges.

Example 1

This example illustrates embodiments of the thermal ink jet inkcomposition using methyl ethyl ketone as the solvent. The materialsemployed in preparing the ink jet ink composition, their amounts inpercentage, and the formulation numbers are set forth in Table 1 below.Nobel DHX 3-4 is a cellulose nitrate resin with a weight averagemolecular weight of about 42,000. Joncryl 682 is a styrene/acryliccopolymer with a weight average molecular weight of about 1700. Ad ProMTS is a sulfonamide-modified epoxy polymer with a weight averagemolecular weight of about 1700. K-Plast 1022 is a urethane polymer witha weight average molecular weight of about 7500. DC Silicone resin is asilicone resin with a weight average molecular weight of about 2500.Poly 4-hydroxy styrene resin is a branched polymer with a weight averagemolecular weight of about 2500. Paraloid B-66 is an acrylic polymer witha weight average molecular weight of about 70,000.

TABLE 1 Material 11903 12217 12418 12419 12461 12463 12464 12465 1247112589 12721 12722 12723 12745 Methyl ethyl 73.35 75.35 75.35 75.35 75.3575.35 75.35 75.35 77.35 85.35 85.45 85.3 85.45 85.35 ketone Joncryl 6824 Ad Pro MTS 4 4 4 4 4 4 K-Plast 1022 4 2 DC Silicone 4 2 2 Resin Nobel2 DHX 3-4 poly 4-hydroxy 2 2 styrene Super Ester 2 A-75 Paraloid B-66 2Propasoll M 10 Propasol P 10 10 10 10 10 10 10 10 10 6 6 6 6 6 Diacetone6 6 6 6 6 6 6 6 Alcohol Silwet-L7622 0.10 0.1 0.1 0.1 0.1 0.1 0.1 0.10.1 0.1 0.1 Silicon Fluid 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.050.05 SF-69 Plasticizer 8 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.50.5 Novec 0.05 0.05 FC-4430 Capstone 0.2 FS-35 Capstone 0.05 FS-3100Orasol Black 3.25 3.25 3.25 3.25 3.25 3.25 3.25 3.25 3.25 3.25 3.25 3.253.25 3.25 RLI Valifast Orange 0.75 0.75 0.75 0.75 0.75 0.75 0.75 0.750.75 0.75 0.75 0.75 0.75 0.75 3210 Viscosity (cPs) 0.94 0.76 0.82 0.820.91 0.80 1.15 0.94 1.11 0.72 0.67 0.70 0.69 0.83 Specific 0.85 0.850.847 0.850 0.840 0.838 0.848 0.843 0.838 0.840 0.839 0.837 0.837 0.842Gravity

Table 2 illustrates the average dry time, decap time, rub resistance,and kogation performance for the ink formulations in Table 1. The inkcompositions were placed in a thermal ink jet cartridge and ink dropletswere ejected for extended periods of time. The drop weights weremeasured periodically using a drop weight tester available from Imtech,Inc. (Corvallis, Oreg.). The onset of kogation is measured as the numberof drops fired before the drop weight is consistently reduced by 10% ormore from the initial drop weight. It can be seen that all of the inkcompositions (except formulations 11903 and 12471) had decap times of atleast 90 seconds and acceptable rub resistance. Additionally, samples12418, 12419, 12461, 12463, 12465, 12471, 12589, 12722 and 12723 allwere sufficiently resistant to kogation to be able to be fired at least25 million drops per nozzle of a thermal ink jet printer before a lossin drop weight of 10%.

TABLE 2 Kogation = drops fired Rub before 10% drop Decap Time Resistanceweight loss (sec, @ 80% on Rub onset Dry Nozzle Aqueous Resistance(million drops) Time Ink Recovery) Coat on PET nozzle) (sec) 11903 15-30Good Good 10-15 <5 12217 >300 Good Good  5-10 >5 12418 90 Good Good >25<5 12419 120 Good Good >25 >5 12461 90 Good Good >25 <5 12463 120 GoodFair >25 <5 12464 210 Good Good 5 <5 12465 210 Good Good >25 >5 1247115-30 Good Good >25 <5 12589 60 Good Good >25 <5 12721 300 Good Good15-20 <5 12722 45 Good Good >25 <5 12723 300 Good Good >25 <5 12745 60Good Good >20 <5

Example 2

This example illustrates embodiments of the thermal ink jet inkcomposition using an ethanol-based solvent. The materials employed inpreparing the ink jet ink composition, their amounts in percentage, andthe formulation numbers are set forth in Table 3 below. Nobel DLX 3-5 isa cellulose nitrate resin available from Nobel Enterprises. MowitalLPB16H is a polyvinyl butyral resin available from Kuraray America.

TABLE 3 Ink # 6259 6271 6272 6273 6320 6321 6322 ethanol 85.45 85.4588.45 88.45 85.35 85.35 87.35 Propasol P 6 6 6 6 6 6 6 poly 4-hydroxy 43 styrene Joncryl 682 4 4 Nobel DLX 3-5 1 Mowital LPB16H 1 Rit-O-Lit MHP1 Super Ester A-75 1 1 Plasticizer 8 0.5 0.5 0.5 0.5 0.5 0.5 0.5Silicone Fluid 69 0.05 0.05 0.05 0.05 0.05 0.05 0.05 Silwet L7622 0.10.1 0.1 Orasol Black RLI 3.25 3.25 3.25 3.25 3.25 3.25 3.25 ValifastOrange 0.75 0.75 0.75 0.75 0.75 0.75 0.75 3210 total 100 100 100 100 100100 100 Viscosity (cPs) 1.73 1.87 1.83 1.99 1.80 2.15 1.58 Surface Ten22.3 22.3 21.6 21.5 20.5 21.4 22.9 (dynes/cm) pH 4.71 5.79 5.95 6.254.88 5.79 5.39 Specific Gravity 0.815 0.821 0.81 0.81 0.828 0.835 0.814

Table 4 illustrates the % loss in drop weight as a function of thenumber of drops fired per nozzle for the ink formulations in Table 3,measured as previously described. It can be seen that formula 6259,6271, and 6322 were sufficiently resistant to kogation to be able to befired at least 10 million drops per nozzle in a thermal ink jet printerwith no more then 10% loss in drop weight.

TABLE 4 Millions of drops fired per % loss in drop weight nozzle 62596271 6272 6273 6320 6321 6322  5M DPN 3.0% 3.0% 1.5% 17.0% 4.3% 7.6%9.6% 10M DPN 10.0% −2.3% 13.2% 46.4% 16.0% 14.9% 7.4% 15M DPN 22.9% 2.2%12.5% 51.7% 24.0% 14.9% 7.4% 20M DPN 30.8% 9.5% 3.4% 54.4% 27.3% 15.2%6.9% 25M DPN 43.8% 7.2% 15.0% 56.5% 42.7% 22.0% 14.1% 30M DPN 41.2%17.9% 22.7% 12.8% Dry Time (s) <5 <5 <5 <5 <5 <5 <5 Decap Time (s) 600300 120 60 120 120 600

All references, including publications, patent applications, andpatents, cited herein are hereby incorporated by reference to the sameextent as if each reference were individually and specifically indicatedto be incorporated by reference and were set forth in its entiretyherein.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. The terms “comprising,” “having,” “including,” and “containing”are to be construed as open-ended terms (i.e., meaning “including, butnot limited to,”) unless otherwise noted. Recitation of ranges of valuesherein are merely intended to serve as a shorthand method of referringindividually to each separate value falling within the range, unlessotherwise indicated herein, and each separate value is incorporated intothe specification as if it were individually recited herein. All methodsdescribed herein can be performed in any suitable order unless otherwiseindicated herein or otherwise clearly contradicted by context. The useof any and all examples, or exemplary language (e.g., “such as”)provided herein, is intended merely to better illuminate the inventionand does not pose a limitation on the scope of the invention unlessotherwise claimed. No language in the specification should be construedas indicating any non-claimed element as essential to the practice ofthe invention.

Preferred embodiments of this invention are described herein, includingthe best mode known to the inventors for carrying out the invention.Variations of those preferred embodiments may become apparent to thoseof ordinary skill in the art upon reading the foregoing description. Theinventors expect skilled artisans to employ such variations asappropriate, and the inventors intend for the invention to be practicedotherwise than as specifically described herein. Accordingly, thisinvention includes all modifications and equivalents of the subjectmatter recited in the claims appended hereto as permitted by applicablelaw. Moreover, any combination of the above-described elements in allpossible variations thereof is encompassed by the invention unlessotherwise indicated herein or otherwise clearly contradicted by context.

1. A thermal ink jet ink composition comprising: one or more volatileorganic solvents, wherein the one or more volatile organic solvents areselected from C₁-C₄ alcohols, C₃-C₆ ketones, C₃-C₆ esters, C₄-C₈ ethers,and mixtures thereof; one or more humectants, wherein the humectants arepresent in an amount not more than 30% by weight of the ink composition;one or more binder resins; and one or more dyes, wherein the inkcomposition is suitable for use in a thermal ink jet printer and whereinthe ink composition has a slow rate of kogation such that it is capableof being printed at least 10 million drops per nozzle from the thermalink jet printer before drop weight of the ink composition is reduced bymore than 10%.
 2. The thermal ink jet ink composition of claim 1,wherein if water is present, it is present in amount up to 10% by weightof the ink composition.
 3. The thermal ink jet ink composition of claim1, wherein the one or more binder resins are selected from cellulosenitrate resins, polyamide resins, rosin ester resins, acrylic resins,polyvinyl butyral resins, vinyl resins, polyhydroxystyrene resins,silicone resins, sulfonamide-modified epoxy resins, sulfonamide-modifiedformaldehyde resins, sulfonamide-modified melamine formaldehyde resins,and combinations thereof.
 4. The thermal ink jet ink composition ofclaim 1 wherein the binder resin has a weight average molecular weightless than 50,000.
 5. The thermal ink jet ink composition of claim 1wherein the binder resin has a weight average molecular weight less than10,000.
 6. The thermal ink jet ink composition of claim 1 wherein thebinder resin has a weight average molecular weight less than 5,000. 7.The thermal ink jet ink composition of claim 1 wherein the binder resinhas a weight average molecular weight less than 3,000.
 8. The thermalink jet ink composition of claim 1, wherein the one or more binderresins are selected from rosin ester resins, polyhydroxystyrene resins,silicone resins, sulfonamide-modified epoxy resins, sulfonamide-modifiedformaldehyde resins, sulfonamide-modified melamine formaldehyde resins,and combinations thereof.
 9. The thermal ink jet ink composition ofclaim 1, wherein the thermal ink jet ink composition has a decap time ofat least 60 seconds and a dry time of less than 5 seconds on anon-porous substrate when used in a thermal ink jet print head.
 10. Thethermal ink jet ink composition of claim 1, wherein the one or morevolatile organic solvents are selected from methanol, ethanol,1-propanol, acetone, methyl ethyl ketone, methyl n-propyl ketone, ethylacetate, propyl acetate, butyl acetate, and mixtures thereof.
 11. Thethermal ink jet ink composition of claim 10, wherein the one or morevolatile organic solvents are selected from methanol, ethanol, methylethyl ketone, and mixtures thereof.
 12. The thermal ink jet inkcomposition of claim 11, wherein the one or more volatile organicsolvents comprise methyl ethyl ketone.
 13. The thermal ink jet inkcomposition of claim 12 wherein the methyl ethyl ketone is present in anamount greater than 70% by weight of the ink composition.
 14. Thethermal ink jet ink composition of claim 10, wherein the one or morevolatile organic solvents comprise ethanol.
 15. The thermal ink jet inkcomposition of claim 14 wherein the ethanol is present in an amountgreater than 80% by weight of the ink composition.
 16. The thermal inkjet ink composition of claim 1, wherein the one or more volatile organicsolvents comprise methyl ethyl ketone and one or both of ethanol andmethanol.
 17. The thermal ink jet ink composition of claim 1, whereinthe one or more humectants are selected from the group consisting ofpolyols, glycol ethers, glycol ether acetate, diacetone alcohol,2-pyrrolidinone, N-methylpyrrolidinone, ethyl lactate, butyl lactate,1,3-dimethyl-2-imidazolidindione, propylene carbonate, alkyl esters, andmixtures thereof.
 18. The thermal ink jet ink composition of claim 1,wherein the one or more dyes are selected from the group consisting C.I.Solvent Black 29, C.I. Solvent Orange 54, and mixtures thereof.
 19. Thethermal ink jet ink composition of claim 1, wherein the ink compositionhas a viscosity of less than 3 cPs.
 20. A thermal ink jet cartridgeincluding the ink of claim
 1. 21. A thermal ink jet ink compositioncomprising: one or more volatile organic solvents present in amount atleast 70% by weight of the ink composition, wherein the one or morevolatile organic solvents are selected from methanol, ethanol,1-propanol, acetone, methyl ethyl ketone, methyl n-propyl ketone, andmixtures thereof; one or more humectants; one or more binder resins,wherein the binder resins are selected from cellulose nitrate resins,polyamide resins, rosin ester resins, acrylic resins, polyvinyl butyralresins, vinyl resins, polyhydroxystyrene resins, silicone resins,sulfonamide-modified epoxy resins, sulfonamide-modified formaldehyderesins, sulfonamide-modified melamine formaldehyde resins, andcombinations thereof; and one or more dyes, wherein if water is present,it is present in amount up to 10% by weight of the ink composition, andwherein the ink composition has a decap time of at least 15 seconds anda dry time of 5 seconds or less on a non-porous substrate when used in athermal ink jet print head and wherein the ink composition has a slowrate of kogation such that it is capable of being printed at least 10million drops per nozzle from the thermal ink jet printer before dropweight of the ink composition is reduced by more than 10%.
 22. Aprinting system comprising: a thermal ink jet cartridge containing athermal ink jet ink composition comprising: one or more volatile organicsolvents present in amount at least 70% by weight of the inkcomposition, wherein the one or more volatile organic solvents areselected from C₁-C₄ alcohols, C₃-C₆ ketones, C₃-C₆ esters, C₄-C₈ ethers,and mixtures thereof; one or more humectants, wherein the humectants arepresent in an amount not more than 30% by weight of the ink composition;one or more binder resins; and one or more dyes, wherein if water ispresent, it is present in amount up to 10% by weight of the inkcomposition; and a thermal ink jet print head comprising a plurality ofresistors for ejecting droplets of the ink composition from thecartridge to a substrate; wherein the ink composition has a decap timeof at least 15 seconds and a dry time of less than 5 seconds on anon-porous substrate when used in the thermal ink jet print head andwherein the ink composition has a slow rate of kogation such that it iscapable of being printed at least 10 million drops per nozzle from thethermal ink jet printer before drop weight of the ink composition isreduced by more than 10%.